The immune mechanisms that lead to specific autoimmune conditions are largely unknown. What we are missing most is a clear description of the steps involved. The anti-Sm response is closely associated with systemic lupus erythematosus (SLE) in man and both induced and genetic models in animals. We have "identified PPPGMRPP as the first humeral epitope in Sm BIB" in patients that develop anti-Sm under observation (but who are already past clinical disease onset). We have also collected 633 sera from 130 individuals who up to nine years later developed SLE. These sera are not replaceable. In ordinary clinical practice no samples are available from before the onset of clinical disease. Indeed, to find such sera would require a project to prospectively collect sera from millions of normal individuals and then retrieve the sera from those who later developed lupus. Fortunately, exactly this has been done in the US military where the Army/Navy Serum Repository has collected over 20,000,000 samples. In the NIAID funded proposal R01 AI31584 to which this current R21 proposal is linked, we identified 130 Active Duty Military with SLE and have obtained their 633 samples and those of 520 matched controls. There are only small volumes of these sera available (about 0.5 ml) and the current technology cannot comprehensively address the question of the earliest structure identified by the immune system. To overcome this technological hurdle, we propose to adapt an optical fiber microsphere technology to determine rigorously whether PPPGMRPP is the first epitope or not. Under the proposed configuration the volume of serum required would be 1500-fold lower than required by our current technology, thereby permitting evaluation of all the overlapping octapeptides of Sm BIB', Sm D1, Sm D2, and Sm D3 with only 1 microliter of this irreplaceable resource and leaving over 99 percent of the resource for other experiments. Theoretically, the first autoimmune epitope has the potential to be critically important. This is the structure against which B cell tolerance (or ignorance) mechanisms are broken and this is the recognition event that all subsequent epitopes are likely to be dependent. In addition, the immune history leading to recognition of this epitope has the potential to reveal the etiology of lupus. These sera present our best opportunity to understand humeral autoimmunity in SLE before diagnosis. Moreover, once the microsphere technology is adapted to this important question, it will be amenable to addressing many other research and marketplace applications.